The present invention relates to a novel vapor phase process and a catalyst useful therefore.
Many catalytic processes employing transition metal complex catalysts are known. Such processes are almost always carried out in batch operation in liquid phase under pressure with the transition metal complex catalyst being dissolved in the liquid reaction medium. When the reaction is completed, the expensive transition metal complex catalyst if it is to be reused, must be separated from the reaction system. Because the catalyst is dissolved in the liquid phase reaction system, this is difficult.
U.S. Pat. No. 4,276,195 to Verkade discloses a technique for overcoming this disadvantage. In accordance with this technique, transition metal complex catalysts are formulated in the form of polymers comprising repeating groups of the transition metal and a suitable bidentate ligand. The transition metal actually forms a part of the polymer chain and hence is firmly bonded into the polymer system. The polymer has a high enough molecular weight so that it is in solid form and exhibits little solubility in the liquid reaction system. Accordingly, the polymer catalyst can be easily removed from the reaction system by filtration or other simple physical separation.
Although use of the Verkade catalysts will reduce or eliminate a number of problems associated with liquid phase batch operations, they nonetheless appear suitable for use only with liquid phase processes. Furthermore, it has been found that these polymers will, over time, at least partially dissolve in the liquid reaction medium, which significantly reduces the advantages of these materials.
Accordingly, it is an object of the present invention to provide a new solid phase catalyst which is based on a transition metal complex as the active catalytic material and which is ideally suited for use in vapor phase heterogeneous continuous reactions.